Abstract
EC, T-N and NO3-N concentrations in stream waters were measured at 6 pasture districts (3 are pasturage areas and 3 are housing areas).
As a result, stocking density of cattle and NO3-N concentration had a high correlation. Nitrogen concentration becomes high with the increase of stocking density of cattle. However the effect of cattle farms on the N concentration of stream water is smaller than pig farms with unlined storage ponds. The effluent rate of nitrogen by cattle is estimated as less than 10%.
Stocking density is limited by feed plants harvest in the pasture areas, and usually the stocking density is low (<2 heads/ha per pasture area), and the N concentration is low (T-N<4.4mg/l, NO3-N <3.0mg/l). Then the influence of non-point sources (upland fields etc.) as noise on the N concentration of stream waters must be considered, and the difference of the amount of precipitation should also be considered. If the precipitation is large, the concentration will decrease.
N concentration of stream water in pasturage areas is lower than that in housing areas. In pasturage areas, there are cattle during the growing season of feed plants and not in winter, so pasturage intensity (CD (Cow Day)/ha or AUD/ha) is more suitable for use than stocking density.
In slurrygation areas, N concentration is lower than in the other areas.
